I have an 04 duramax with a plastic fuel tank, something is leaking down the fuel tank but it does not smell like diesel. It has turned into a good sized puddle under the truck. I don't want to pull the tank yet to find out what it could be. Anyone have any ideas?

The only thing that could be leaking down your tank is diesel, or possibly brake fluid. You may have a cracked or rusted out brake line. Im assuming its leaking out overnight while your truck is parked, so its probably diesel. Are you noticing lower mpgs? is your brake fluid getting low. Check all your fluids , top them off, and figure out whats coming out. Or maybe you got snow in your bed this past week and its melting haha.

I ended up getting a chance to look into it again after a lot of fluid had drained out of it today and checked the brake fluid... Turns out its the brake line popped right above the tank. What a great design Chevy did on designing that placing the line where water and snow will sit up there forever. It did throw me off how much was leaking after it had just sat there.

I ended up getting a chance to look into it again after a lot of fluid had drained out of it today and checked the brake fluid... Turns out its the brake line popped right above the tank. What a great design Chevy did on designing that placing the line where water and snow will sit up there forever. It did throw me off how much was leaking after it had just sat there.

I'm glad to see you've pinpointed your problem. First off, whether your fixing it or having it fixed, brake fluid is EXTREMELY corrosive. Clean where it was leaking, especially painted surfaces, after one day of sitting on my old junker (powerstroke) I could remove the paint by rubbing it with my fingers. So be careful haha. Also that brake line may be easier to replace by removing the bed. (8 bolts underneath and a few wiring connectors.) Good luck!

I bought a 5-6 foot piece of brake line and two compression fittings to fix this problem on my truck. Apparently using compression fittings on brake lines will fail PA inspection if it is seen, but being between the bed and fuel tank they can't be seen and I have not had any problems with them for over a year.

Register Now

In order to be able to post messages on the Chevy and GMC Duramax Diesel Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:

Password

Please enter a password for your user account. Note that passwords are case-sensitive.

Password:

Confirm Password:

Email Address

Please enter a valid email address for yourself.

Email Address:

Log-in

User Name

Remember Me?

Password

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.

AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.